Stellar Lifecycles by Anthony J Crowley, demon
1 - Irreversible Collapse
Tell me about the stars, Crowley. (You are my safe place to ask questions, Crowley. I have so many of them). How were they made? How do they live? (Surely there is worship in understanding Godâs marvels? After all, the beauty of a good book isnât just in the pleasure to the eyes, the pretty arrangement of words on the page. The pleasure is in the way the soul gazes into the mirror and comes to know itself better. Let me know the heavens better. Let me know you better.)
Iâll tell you, angel. God created the universe in heat and light, and then She created the angels to weave it. We took the light and moulded it in our hands, pressed it into protons and neutrons, tiny buzzing electrons, and then we pressed those together, too. She called them hydrogen atoms and we gathered them up in our arms into great luminous clouds. Then comes the neat bit, angel, the real trick. The Almighty looked at the way the bits of the atoms stuck together, and said, âlike that, but for big things,â and She called it gravity.
But how does gravity make a star?
Itâs like a hill, you see. Or more like a valley. You put the cloud at the top and gradually, itâll all fall down.
(Apples fall. Angels, too. Does a fall always end in fire?)
Those atomsâll get closer together, it all starts to get hot. And you know, itâs still just a cloud at that point, swirling around in space and all that, but eventually, it gets dense enough that its own mass takes over, and it starts to collapse in on itself. It starts to collapse, right, and you canât stop it. After that point, the star is going to get born come what may. Itâs inevitable.
Well, and then things get hotter and hotter until⌠See, making hydrogen nuclei is easy, in the grand scheme of things. Take a proton, right? That's basically it. Sometimes add a neutron. 'S not that hard. The leap from hydrogen to helium, though, that's a thing. Takes a whole boatload of energy to force four of those recalcitrant little bastards to share space in a nucleus.
They don't just⌠attract? (Like you and I? Tell me we're just another law of nature, an inevitable binding.)
They get close enough, they do. Almost impossible to separate, eventually. But to start with, no. Something has to force them together, some external circumstance. Something like the heat generated in a collapsing gas cloud.
(Something like a conversation on a wall, an unexpected moment of kinship, the way my stomach swooped like a swallow when you smiled at me, close, close, under my wing.)
So, it gets hot enough to push the hydrogen nuclei together to form helium, but the really clever bit comes next, because, angel, get this. When they fuse, they actually release more energy. It's like Creation in miniature. Happens fast, too. BOOM. And suddenly your nice innocuous little gas cloud is a fiery ball of nuclear fusion.
After that, you've got a main sequence star, happy to shine away for however long. Millions of years, probably, if She'd let it.
The atoms stop falling inwards? (Tell me there's an end, a soft landing. Surely it can't go on forever.)
For now. Gravity's still pulling them in, but the force of the fusion is also trying to push them back out.
Exactly. Both sides are equally matched. No one's going anywhere. The forces are balanced.
You⌠yeah. You could say that.
It doesnât last, though. It canât.
Why not? (If you donât rock the boat, if youâre careful, surely nothing needs to change.)
All good things, angel, you know what they say. The star runs out of hydrogen, converts it all to helium, so thereâs nothing left to burn. Itâs like letting go of the rope in that tug of war. Gravity wins out, and hard. The star collapses in on itself, heats up again, until suddenly itâs hot enough to start fusing helium.
Oh, a daring rescue? (Tell me, tell me thereâs a hero at the eleventh hour. Tell me thereâs a safe way to proceed.)
Not... exactly. Not precisely, no. âCause the same thing happens all over again -- the helium runs out, gravity wins, the star collapses and heats up until itâs hot enough to start burning the next biggest element. And so on and so forth. It just sort of wobbles about like that, expanding and contracting, clinging on desperately to life, until itâs burned through everything it can.
It sounds positively awful.
Perhaps, in a way. Thereâs something beautiful to it, too, though. Symphonic, almost. The layers of elements that build up like tree rings, the way it flings out its coronal envelope while the core is slowly collapsing, like a robin puffing up its chest feathers. Red giants, the humansâll call them, and theyâre magnificent.
No, I know, but-- this stage is important, because this is where the complex elements come from. Iron for blood, oxygen for air, carbon for-- everything. You canât have life without this stage, angel. The star has to start to die for everything else to begin.
And thatâs the end of it? Nucleogenesis completed? Do we⌠do we simply mourn the starâs noble sacrifice, and move on?
Not in the least, angel. How do you think the elements get out of the star to make life?
A big-- really big explosion. Massive. As much light given off as an entire galaxy.
Oh, like the one we saw at Bethlehem. What did you call it?
A supernova. Exactly. Not all stars go out that way. Not the smaller ones. The sun will go with a bit less fanfare, just shut off the power and go dark one day. But the bigger ones, the ones with sufficient mass, they go up like a firework, like an atom bomb.
With a bang, rather than a whimper. I suppose you approve.
If youâve got to go, go with style, thatâs what I always say.
Yes, I am aware. (That's what I'm afraid of.) And after that?
Depends on the mass again. Thereâs always something left behind, some compact little memory of what went before. Might be a white dwarf or a neutron star. With sufficient mass, it can lead to a black hole. Even they serve their purpose, though. Most galaxies have them, right at the very centre. The dark heart of the cosmos.
Surely, this must be the end.
No, angel. Not even close.
âI helped make this one,â Crowley said quietly. âWasnât much of an angel, but I enjoyed the work.â
âYou should be proud,â Aziraphale said. âItâs incredible, my dear. Tell me about it?â
âItâs a stellar nursery, a place where new stars are born. Dâyou remember what I told you that time, about how stars live and die?â
âHow could I forget?â
âRight. Well,â Crowley said, shifting a little, caressing Aziraphaleâs fingers restlessly. âAfter the fusionâs stopped and the starâs gone cold, or exploded or whatever itâs going to do, the molecules thatâre left over eventually form a nebula. Over time, gravity does its work again, and the densest bits of the cloud pull in more and more matter, until theyâre dense enough to collapse into a protostar. At critical density, fusion starts all over again.â
âBobâs your uncle.â
âBobâs yourâŚâ Crowley shook his head. âNevermind. Point is, a star died, and a new star was born. Itâs different to what came before, more complex in its make-up maybe, but just as⌠just as precious.â
{excerpts from Starstuff, written by @themoonmothwritesâ/the_moonmoth, illustrated by me/cassieoh for the Good Omens Big Bang 2019}
